Control Crossgen2 optimizations with DebuggableAttribute (#44514)

Control Crossgen2 optimizations with DebuggableAttribute (#44514)

* Assemblies compiled in debug configuration use the `System.Diagnostics.DebuggableAttribute` to indicate optimizations are disabled.
* Match Crossgen 1's behavior and respect this setting if no explicit optimization arguments are passed in.
* Add `-Od` switch to disable optimizations since now the default behavior of Crossgen2 is to optimize release-built assemblies.
* Fix runtime assert when checking the GC ref map for multi-dimensional array's intrinsic `Address` method on x86. `Address` has a custom calling convention which always requires the extra param type in the signature. The extra shared generic check is too restrictive and doesn't match what we tell the JIT the signature is in https://github.com/dotnet/runtime/blob/4b8d10154c39b1f56424d4ba2068a3150d90d475/src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs#L500.